diff --git a/phpstan-baseline.php b/phpstan-baseline.php
index 8d647f40e497..1493398334c1 100644
--- a/phpstan-baseline.php
+++ b/phpstan-baseline.php
@@ -1146,11 +1146,6 @@
 	'count' => 1,
 	'path' => __DIR__ . '/system/Database/Migration.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Property CodeIgniter\\\\Database\\\\Migration\\:\\:\\$DBGroup \\(string\\) on left side of \\?\\? is not nullable\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/system/Database/Migration.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Construct empty\\(\\) is not allowed\\. Use more strict comparison\\.$#',
 	'count' => 8,
diff --git a/system/Database/Migration.php b/system/Database/Migration.php
index 1616830f9267..f12509d6264a 100644
--- a/system/Database/Migration.php
+++ b/system/Database/Migration.php
@@ -21,7 +21,7 @@ abstract class Migration
     /**
      * The name of the database group to use.
      *
-     * @var string
+     * @var string|null
      */
     protected $DBGroup;
 
@@ -39,12 +39,15 @@ abstract class Migration
      */
     protected $forge;
 
-    /**
-     * Constructor.
-     */
     public function __construct(?Forge $forge = null)
     {
-        $this->forge = $forge ?? Database::forge($this->DBGroup ?? config(Database::class)->defaultGroup);
+        if (isset($this->DBGroup)) {
+            $this->forge = Database::forge($this->DBGroup);
+        } elseif ($forge !== null) {
+            $this->forge = $forge;
+        } else {
+            $this->forge = Database::forge(config(Database::class)->defaultGroup);
+        }
 
         $this->db = $this->forge->getConnection();
     }